The present invention relates to a method of generating a phase shifted clock pulse signal which is shifted in phase by a phase value that can be set as desired between zero and -.pi., particularly a high frequency clock pulse signal, employing conventional continuous phase shifters which can be set between zero and -.pi./2 and -3.pi./4, respectively, with the frequency of the original signal (T) being divided in half by means of a frequency divider and generating phase shifts of this frequency-halved signal being generated at 0, -.pi./2 and -.pi.. According to the method two such controllable phase shifters each generate a signal and are continuously adjustable in phase to a value in a range between the phase of the first input signal and the phase of a second input signal in such a manner that the first phase shifter is fed at its first input with the undelayed frequency-halved signal and at its second input with the frequency-halved signal shifted in phase by -.pi./2; and the second phase shifter is fed at both its inputs with the frequency-halved signal which is shifted in phase by -.pi./2 and -.pi., respectively, both phase shifters being controlled jointly by a control voltage (u.sub.r) to thus be able to generate any desired, predeterminable, continuous phase values in a range from 0 to -.pi./2 and from -.pi./2 to -.pi., with thereafter the frequency of the thus phase shifted signals being doubled again so that phase shift values between 0 and -.pi. with reference to the frequency of the original signal (T) result. That the output and/or input signals of the two controllable phase shifters are each filtered in a lowpass filter in such a manner that possibly existing harmonics are attenuated in amplitude with respect to the frequency-halved signal.
The present invention also relates to a circuit arrangement for generating a clock pulse signal, particularly a high frequency clock pulse signal, which is shifted in phase by phase values which can be set as desired between 0 and -.pi. by employing phase shifters each able to generate a signal whose phase can be continuously adjusted to a value in a range between the phase of a first input signal and the phase of a second input signal, with a master-slave D-flip-flop supplemented by an inverted feedback so as to form a ring being provided as the frequency divider to whose clock pulse input the signal (T) to be shifted is fed. Either the master or the slave output signals exhibit phase shifts of 0 and -.pi. while the other of the master and slave output signals exhibits the phase value -.pi./2, with two phase shifters being provided. In a circuit of this type, the phase shifters are controlled jointly by one control signal (u.sub.r), the two inputs of the one phase shifter are charged by the undelayed frequency-halved signal and by the frequency-halved signal delayed by -.pi./2, respectively, the two inputs of the other phase shifting member are charged by the frequency-halved signal delayed by -.pi./2 and -.pi., respectively, an exclusive OR member is provided whose inputs are connected with the outputs of the two phase shifters and the output signal of the exclusive OR member is the desired signal which is shifted in phase by a value within a range from 0 to -.pi. with reference to the phase and frequency of the input signal (T). The invention also relates to a similar circuit arrangement but wherein a reset flip-flop is provided instead of the exclusive OR member and has an inverting input and an inverting output and inputs which are connected with the outputs of the two phase shifters, and the inverted or the non-inverted output signal of the flip-flop is the desired signal which is shifted in phase by a value within a range from 0 to -.pi. and from -.pi. to -2.pi., respectively, with reference to the phase and frequency of the input signal (T).
One possible use of such a method and apparatus is for electrical regenerators in optical transmission systems.
Phase shifters of the customary type permit phase shifts in a range from 0 to about -120.degree.. Also see the article "An Undersea Fiberoptic Regenerator Using an Integral Substrate Package and Flip-Chip SAW Mounting" by Dawson and Rogerson, Journal of Lightwave Technology, Vol. LT-2, No. 6, December, 1984, pages 926-932.
The invention provides a method and a circuit arrangement which are able to continuously perform phase shifts in a range between 0 and -.pi. over a broad frequency range without it being necessary to tune the circuit. With customary phase shifters, the circuit must be matched in each case--even in the above-mentioned Dawson and Rogerson publication--to the signal frequency.
The method and the circuit arrangement permit any desired continuous phase shift in a range between 0 and -.pi., with the costs for this being relatively low. This requires neither internal matching nor external elements, for example delay lines, which would each have to be adapted to the signal frequency, for example by appropriately setting the length of a delay line. Rather, the phase shift occurs nearly independently of the signal frequency. This results in a further advantage over conventional phase shifters, namely simple monolithic integratability of the circuit, which leads to a considerable reduction in costs.